JP2618947B2 - Positive photoresist composition - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive photoresist composition, and more particularly, to a dimensional accuracy and a pattern suitably used for manufacturing a semiconductor integrated circuit device such as an VLSI. The present invention relates to a positive photoresist composition for forming a fine pattern having an excellent shape and good heat resistance.

2. Description of the Related Art In recent years, in the semiconductor industry, the demand for industrial computers, office automation, personal computers, and the like has increased dramatically, and the technology has continued to evolve rapidly. , The density and the degree of integration are rapidly increasing. Also, in forming a fine pattern, the pattern width of a semiconductor integrated circuit device for a 256 kilobit DRAM is about 2 μm.
With the integration of 1.0-1.3 .mu.m for 1-Mbit DRAMs and 0.7-0.8 .mu.m for 4-Mbit DRAMs, so-called sub-micron order fine processing technology has become necessary.

At present, pattern formation in the manufacture of semiconductor integrated circuit devices is performed by photolithography, and positive type photoresists are widely used for fine processing with a pattern width of about 2 μm or less.

The positive photoresist is usually composed of a novolak resin soluble in an alkali solution and a photolytic component called a photosensitizer. Examples of the novolak resin soluble in an alkali solution include, for example, a phenol-formaldehyde novolak resin (US Pat. 3402044) and cresol novolak resin (“Electrochemical and Industrial Physical Chemistry”, Vol. 48, p. 584 (1980)). Furthermore, by appropriately selecting the proportion of cresol isomers during the production of the cresol novolak resin, a highly sensitive positive photoresist (JP-A-58-17112) or a positive photoresist having excellent dimensional accuracy (ex. JP-A-62-35349) is also known.

On the other hand, as photosensitizers, for example, sulfonate esters of naphthoquinonediazidosulfonic acid, which is a photodecomposition component, and a compound having a phenolic hydroxyl group, etc., are widely used, and various types of such esters have been proposed. (U.S. Pat. Nos. 3,046,118, 3,106,465, 3,148,983,
JP-B-62-28457).

Several methods have been proposed to form a submicron-order pattern using such a positive photoresist, but a method using a reduction projection exposure apparatus (hereinafter, referred to as a stepper) among them is generally used. And
At present, as the stepper, a stepper using a G line having a wavelength of 436 nm is mainly used. However, this G
Although a line stepper can form a pattern of about 0.8 to 1.0 μm, it cannot be used for a demand for a pattern width smaller than that associated with recent high integration. Steppers have been developed which output short-wavelength 365 nm mercury radiation I-rays.

In photolithography for forming such a pattern on the order of submicrons, the improvement of the stepper as described above and the development of a positive type photoresist corresponding to the stepper are also important topics. As for this positive photoresist, it is generally known that a positive photoresist corresponding to a G-line stepper can also be used in an I-line stepper [“Solid State Technology” (solid state technology).
technology) "Nippon Board, February issue, pages 34-38 (19
1987). However, if a positive photoresist conventionally used for a G-line stepper is used for an I-line stepper, the I-line is more likely to be absorbed into the positive-type photoresist and to be excessively absorbed than the G-line, resulting in a positive photoresist. The problem is that the resist pattern having a cross-sectional shape excellent in vertical pattern dimensions cannot be obtained, especially because the cross-sectional shape of the resist is degraded, and a resist pattern having a cross-sectional shape excellent in the vertical pattern dimension is obtained. There is a strong demand for the development of a resist that can obtain a uniform cross-sectional shape.

In addition, in the etching processing of a substrate on the order of submicron, which is performed using a resist pattern formed on the substrate by a lithographic technique using a G-line stepper or an I-line stepper as a mask, plasma with a small amount of side etching is usually used. Dry etching has been performed. In this dry etching method, the resist pattern as a mask is also damaged during etching of the substrate, and the film is gradually reduced, but even if the resist pattern is reduced, the substrate to be etched accurately corresponds to the mask turn. It is necessary to form a reproduced pattern. In order to reduce this film loss, it is usually effective to increase the post-bake temperature after development.
The resist pattern must have excellent sectional shape and also have heat resistance.

However, conventional positive photoresists lack any of these required characteristics and are not always satisfactory.

Problem to be Solved by the Invention Under such circumstances, the present invention can be applied to both the G-line stepper and the I-line stepper, has excellent dimensional accuracy and pattern shape, and has good heat resistance. An object of the present invention is to provide a positive photoresist composition capable of forming a fine pattern.

Means for Solving the Problems The present inventors have conducted intensive studies to develop a positive photoresist composition having the above-mentioned excellent characteristics,
It has been found that the purpose can be achieved by combining a specific cresol novolak resin with a specific photosensitizer, and based on this finding, the present invention has been completed.

That is, the present invention provides a positive photoresist composition comprising (A) a cresol novolak resin and (B) a photosensitizer containing a naphthoquinonediazidesulfonic acid ester as a main component. Using, as the resin, a resin obtained from a cresol mixture of 10 to 45% by weight of m-cresol and 90 to 55% by weight of p-cresol; and (b) 2,3,4-triol as the photosensitizer For 1 mole of at least one polyhydroxybenzophenone selected from hydroxybenzophenone, 2,3,4,4'-tetrahydroxybenzophenone and 2,2 ', 4,4'-tetrahydroxybenzophenone, 2-Naphthoquinonediazide-4-sulfonic acid and 1,2-naphthoquinonediazide-5-sulfonic acid in a weight ratio of 20:80 to 80:
Naphthoquinonediazide sulfonic acid containing at a ratio of 20 is reacted at a ratio of 2.5 times or more, and an esterification reaction product having a polyester content of at least 80% by mole is used. To provide a positive photoresist composition.

 Hereinafter, the present invention will be described in detail.

In the composition of the present invention, the cresol novolak resin used as the component (A) must be obtained from a cresol mixture of 10 to 45% by weight of m-cresol and 90 to 55% by weight of p-cresol. It is. Heat-resistant,
This proportion is an indispensable condition to obtain a positive photoresist excellent in dimensional accuracy and pattern shape,
With a cresol novolak resin obtained from a resin whose ratio is out of the above range, a composition that can satisfy both the heat resistance of a practical photoresist and the pattern cross-sectional shape cannot be obtained.

The photosensitizer containing naphthoquinonediazidesulfonic acid ester as a main component used as the component (B) in the composition of the present invention comprises 2,3,4-trihydroxybenzophenone, 2,3,4,4'-tetrahydroxy It is an esterification reaction product of at least one polyhydroxybenzophenone selected from benzophenone and 2,2 ', 4,4'-tetrahydroxybenzophenone with naphthoquinonediazidesulfonic acid. It is preferable that all the hydroxyl groups of the polyhydroxybenzophenone are esterified by an esterification reaction. However, in practice, it is sufficient if the content of polyesters equal to or higher than triesters is 80 mol% or higher. Can be used. If the content is less than 80 mol%, the dimensional accuracy and pattern shape of the obtained resist pattern will be reduced, and the heat resistance will also be significantly deteriorated.

Further, naphthoquinonediazidesulfonic acid used in the present invention is 1,2-naphthoquinonediazide-4-sulfonic acid and 1,2-naphthoquinone-5-sulfonic acid in a weight ratio of 20:
It is a mixture containing 80 to 80:20, preferably 40:60 to 60:40. If the mixing ratio is outside the above range, a resist pattern excellent in both heat resistance and cross-sectional shape of the pattern cannot be obtained.

Such photosensitizers were selected from 2,3,4-trihydroxybenzophenone, 2,3,4,4'-tetrahydroxybenzophenone and 2,2 ', 4,4'-tetrahydroxybenzophenone. 1,2-Naphthoquinonediazide-4-sulfonyl chloride and 1,2-naphthoquinonediazide-5-sulfonyl chloride are added in an amount of at least 2.5 moles per mole of at least one kind of polyhydroxybenzophenone. In the presence of a dehydrochlorination catalyst, and then reacted in an inducing solvent, or alternatively, the polyhydroxybenzophenone and 1,2-naphthoquinonediazide-4-sulfonyl chloride and 1 , 2-Naphthoquinonediazide-5
-Sulfonyl chloride may be separately reacted in the same manner as described above, and then the resulting esterification reaction product may be mixed at a predetermined ratio to produce the compound. In the esterification reaction between polyhydroxybenzophenone and naphthoquinonediazidosulfonyl chloride, the esterification ratio varies depending on the reaction solvent, the type of acid catalyst, and the amount of the consumables. Therefore, the reaction materials polyhydroxybenzophenone and naphthoquinonediazidosulfonyl chloride are used. It is desirable to appropriately select conditions depending on the combination of chlorides. Needless to say, a desired ester can be selectively obtained also by purifying a reaction product. The esterification rate can be determined by liquid chromatography.

Regarding the mixing ratio of the cresol novolak resin of the component (A) and the photosensitizer of the component (B) in the composition of the present invention, 10 to 30 parts by weight of the component (B) is added to 100 parts by weight of the component (A). When the amount is less than 10 parts by weight, dimensional accuracy, pattern shape, heat resistance, etc. are inferior, and the object of the present invention may not be sufficiently achieved, and when it exceeds 30 parts by weight. This is not preferable because sensitivity tends to decrease.

The composition of the present invention is preferably used in the form of a solution obtained by dissolving the cresol novolak resin (A) and the photosensitizer (B) in a suitable solvent.

Examples of such solvents include ketones such as acetone, methyl ethyl ketone, cyclohexanone, and isoamyl ketone: monomethyl ether, monoethyl ether, monopropyl ether of ethylene glycol, propylene glycol, ethylene glycol monoacetate, diethylene glycol or diethylene glycol monoacetate; Polyhydric alcohols such as monbutyl ether or monophenyl ether and derivatives thereof: cyclic ethers such as dioxane; and esters such as methyl acetate, ethyl acetate, and butyl acetate. These may be used alone or as a mixture of two or more.

In the positive photoresist composition of the present invention, more compatible additives such as additional resins, plasticizers, stabilizers or coloring agents for making the developed image more visible are commonly used. Can be added.

As an example of a preferred method of using the composition of the present invention, a solution prepared by dissolving the aforementioned cresol novolak resin and a photosensitizer in a suitable solvent is applied to a substrate such as a silicon wafer using a spinner or the like. After drying to form a photosensitive layer, exposure is performed through a required mask using a G-line or I-line stepper. Next, when this is developed using a developing solution, for example, an aqueous solution of 2 to 5% by weight of tetramethylammonium hydroxide or choline, a portion solubilized by exposure is selectively dissolved and removed, and the mask pattern is faithfully adhered. Image can be obtained.

Effects of the Invention The positive photoresist composition of the present invention uses, as a cresol novolak resin, one obtained from a mixed cresol in which the mixing ratio of m-cresol and p-cresol is in a specific range, and By using a mixed naphthoquinonediazide sulfonic acid ester having an esterification rate, it can be applied to either a G-line or an I-line stepper to obtain a resist pattern excellent in dimensional accuracy and pattern shape, and also excellent in heat resistance. LS
It can be suitably used for manufacturing semiconductor integrated circuit devices such as I.

Examples Next, the present invention will be described in more detail with reference to Examples.
The present invention is not limited in any way by these examples.

The properties shown in each example were evaluated by the following methods.

(1) Sensitivity: The sensitivity was shown as the minimum exposure time (ms) required to completely resolve only the pattern of the exposed portion of 1.0 μm.

(2) Cross-sectional shape: The exposure pattern of 1.0 μm was cut in the width direction, the cross-section was observed with a microscope, and the cross-section was classified and shown according to FIGS. 1 to 3 of the accompanying drawings.

(3) Heat resistance: The resist pattern was gradually heated to indicate the temperature immediately before sagging.

Reference Example 1 2.0 g of 2,3,4-trihydroxybenzophenone, 20.0 g of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 1,2-naphthoquinonediazide-4 in 30 ml of dioxane
-8.0 g of sulfonyl chloride was added and dissolved, and 20 g of a 25% by weight aqueous solution of sodium carbonate was further added as a solvent.
After reacting at 5 ° C for 2 hours, dilute hydrochloric acid solution obtained by diluting 25 g of 35 wt% hydrochloric acid with 1,000 g of ion-exchanged water is added to the reaction solution to precipitate a reaction product, and the obtained precipitate is thoroughly washed with ion-exchanged water. After washing, the product obtained by drying was purified, whereby 7.5 g of naphthoquinonediazidesulfonic acid ester having a triester content of 90 mol% was obtained.

Reference Example 2 A mixture (a) of naphthoquinone-1,2-diazido-5-sulfonyl chloride and naphthoquinone-1,2-diazide-4-sulfonyl chloride at a weight ratio of 70:30 or 40:60 by weight.
Using the mixture (b) of 2,3,4-
An esterification reaction was carried out with trihydroxybenzophenone to produce a naphthoquinonediazidosulfonic acid ester having a triester content of 90 mol%.

Reference Example 3 A mixture of naphthoquinone-1,2-diazido-5-sulfonyl chloride and naphthoquinone-1,2-diazide-4-sulfonyl chloride in a weight ratio of 60:40 (a), a mixture in a weight ratio of 30:70 ( b) or using a mixture (c) in a weight ratio of 50:50,
2.0 g of 2,3,4,4'-tetrahydroxybenzophenone and 28.0 g of each of the above mixtures (a), (b) and (c)
All were subjected to an esterification reaction in the same manner as in Reference Example 1 except that a naphthoquinonediazidesulfonic acid ester having a triester content of 85 mol% was produced.

Reference Example 4 Using a mixture of naphthoquinone-1,2-diazido-5-sulfonyl chloride and naphthoquinone-1,2-diazide-4-sulfonyl chloride in a weight ratio of 50:50, 2,2 ', 4,4' −
2.0 g of tetrahydroxybenzophenone and the above mixture 28.0
The esterification reaction was carried out in the same manner as in Reference Example 1 except that g was used, to produce a naphthoquinonediazidesulfonic acid ester having a triester content of 90%.

Comparative Reference Example Using a mixture of naphthoquinone-1,2-diazido-5-sulfonyl chloride and naphthoquinone-1,2-diazido-4-sulfonyl chloride in a weight ratio of 50:50, 2,3,4-trihydroxybenzophenone The esterification reaction was carried out in exactly the same manner as in Reference Example 1 except that the amount of used was changed to 2.5 g.
A naphthoquinonediazidosulfonic acid ester having a triester content of 75 mol% was produced.

Example 1 110 parts by weight of 30% formalin and 5 parts by weight of oxalic acid were added to a mixture of 40 parts by weight of m-cresol and 60 parts by weight of p-cousol, heated to boiling for 100 minutes, and then dehydrated and concentrated under reduced pressure. Thus, a cresol novolak resin was produced.

Then the cresol novolak resin thus obtained
In 100 parts by weight, 20 parts by weight of naphthoquinonediazide sulfonic acid esrel obtained in Reference Example 1 was dissolved in 390 parts by weight of ethylene glycol monoethyl ether acetate, and the solution was filtered using a membrane filter having a pore diameter of 0.2 μm. A photoresist composition was prepared. The photoresist composition was uniformly coated on a 4-inch silicon wafer to a thickness of 1.3 μm using a resist coater TR-4000 (manufactured by Tatsumo), and then dried with a hot plate tablet at 110 ° C. for 90 seconds. Next, G-line reduction projection exposure system DSW-480
G-line exposure was performed using a 0-type wafer stepper (manufactured by GCF) through a test chart mask (manufactured by Dai Nippon Printing Co., Ltd.), followed by development with a 2.38 wt% aqueous solution of tetramethylammonium hydroxide at 23 ° C. for 60 seconds. .

As a result, the sensitivity was 400 ms. Further, the resist pattern had a good cross-sectional shape as shown in FIG. 1 of the accompanying drawings in which the side surface was stood vertically, and the dimensional accuracy was excellent. The heat resistance obtained as the temperature immediately before the sagging of the resist pattern shape was 140 ° C.

Examples 2-6, Comparative Examples 1-2 Except that the mixing ratio of m-cresol and p-cresol and the type and amount of naphthoquinonediazidosulfonic acid ester to be used were as shown in Table 1, except that By repeating the same operation as in Example 1, a positive photoresist composition having the physical properties shown in Table 1 was obtained.

Examples 7 to 11 The mixing ratio of m-cresol and p-cresol and the type and amount of naphthoquinonediazidesulfonic acid ester to be used were as shown in Table 2, and reduction for I-line was performed as an exposure treatment. Except for using a projection exposure apparatus NSR-1010i3 (manufactured by Nikon Corporation), the same procedures as in Example 1 were performed to evaluate the sensitivity, the cross-sectional shape of the pattern, and the heat resistance of each photoresist composition. The results are shown in Table 2. As a result, the photoresist composition of the present invention
It was confirmed that the line reduction projection exposure apparatus could be used effectively, and the heat resistance and the cross-sectional shape of the pattern were extremely excellent.

Example 12 m-cresol and p-kusol were mixed in a weight ratio of 40:60.
Of cresol novolak resin obtained by condensation in a conventional manner using an oxalic acid catalyst, 2.0 g of 2,3,4-trihydroxybenzophenone and 1 g of 1,2-Naphthoquinonediazide-5 sulfonate 5 parts by weight (triester content 90%) obtained by subjecting 7.0 g of 2,2-naphthoquinonediazide-5-sulfonyl chloride to an esterification reaction by a known method. And 2,3,
1,2-naphthoquinonediazide-4-sulfonic acid ester 5 obtained by subjecting 2.0 g of 4-trihydroxybenzophenone and 7.0 g of 1,2-naphthoquinonediazide-4-sulfonyl chloride to an esterification reaction by a known method. And 390 parts by weight of ethylene glycol monoethyl ether acetate, and then filtered using a membrane filter having a pore size of 0.2 μm to prepare a photoresist composition. When a resist pattern was formed from this photoresist composition in the same manner as in Example 1, the minimum exposure time required for complete resolution of only the pattern of the exposed portion having a width of 1.0 μm was 480 ms. The addition drawings show various cross-sectional shapes of the resist pattern, and the resist pattern shape in this example has a good cross-sectional shape in which the side faces are stood vertically as shown in FIG. 1 and has excellent dimensional accuracy. Was. The heat resistance obtained as the temperature immediately before the resist pattern shape sags is 145 ° C.
It was.

Example 13 The exposure apparatus was an I-line reduced projection exposure apparatus which was NSR-1010i3.
A resist pattern was formed in the same manner as in Example 12 except that (Nikon Corporation) was used, and the same results as in Example 12 were obtained.

[Brief description of the drawings]

1 to 3 are cross-sectional views showing different cross-sectional shapes of the photoresist pattern.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Nobuo Tokutake 817-3 Kotani, Samukawa-cho, Koza-gun, Kanagawa Prefecture (72) Inventor Hidekatsu Ohara 1-5-21 Tokumazaka, Chigasaki-shi, Kanagawa Prefecture 21 (72) Inventor Toshimasa Nakayama 26-takamura, Hiratsuka-shi, Kanagawa 26-404 (56) References JP-A-62-35349 (JP, A) JP-A-62-270951 (JP, A) JP-A-60-133446 (JP) JP-A-61-7835 (JP, A) JP-A-62-284354 (JP, A)

Claims (1)

(57) [Claims] (A) a cresol novolak resin,
(B) a positive photoresist composition containing a photosensitizer containing a naphthoquinonediazidesulfonic acid ester as a main component; (a) 10 to 45% by weight of m-cresol and p-cresol 90 as the reasol novolak resin. And (b) as the photosensitizer, 2,3,4-trihydroxybenzophenone, 2,3,4,4'-tetrahydroxybenzophenone and 1,2-naphthoquinonediazide-4-sulfonic acid and 1,2-naphthoquinonediazide per mole of at least one polyhydroxybenzophenone selected from 2,2 ', 4,4'-tetrahydroxybenzophenone -5-sulfonic acid in a weight ratio of 20:80 to 80:
Naphthoquinonediazide sulfonic acid containing at a ratio of 20 is reacted at a ratio of 2.5 times or more, and an esterification reaction product having a polyester content of at least 80% by mole is used. Positive photoresist composition.